Download Chapter 5: Electrons In Atoms

Chapter 5:
Electrons In Atoms
Bohr Model of the Atom
 Bohr proposed that an electron is found only in specific
circular paths, or orbits, around the nucleus.
 Each orbit has a fixed energy
 The fixed energy an electron can have are called energy
levels
Energy and Electrons
 Electromagnetic Radiation
 Electromagnetic radiation consists of oscillating electric and
magnetic fields that are perpendicular to each other.
 Electromagnetic radiation is a result of the motion of
electrically charged particles (specifically electrons)
Waves
 Electromagnetic radiation travels in
waves
 Characteristics of waves
 Amplitude: height of wave
 Wavelength (): distance from crest to crest
of waves
 Frequency (): number of wave cycles in a
period of time (Hertz)
 Speed (c): all EM radiation travels at the
speed of light when in a vacuum
Waves
Waves
 = c/ 
 wavelength is inversely proportionate to frequency
 as wavelength increases; frequency decreases and vice versa
 E=h
 Energy is directly proportionate the frequency
 As frequency increases; energy increases
Forms of Electromagnetic Radiation
 Radio waves
 Microwaves
 Infrared waves
 Visible (ROY-G-BIV)
 Ultraviolet
 X-Rays
 Gamma Rays
EM Spectrum
Spectrum of light
 Spectrum of light
 Sunlight is a combination of all frequencies of visible light
 When sunlight is passed through a prism, the different
frequencies of light separate into a spectrum of colors.
Atomic emission spectra
 When atoms absorb energy, electrons move into higher energy
levels, and these electron lose energy by emitting light when they
return to lower energy levels.
 Ordinary light is a mixture of all wavelengths, but light emitted by
atoms consists of a mixture of only specific frequencies.
 These specific wavelengths are represented by a specific colors
 When the light is separated it gives distinct lines and creates an
atomic emission spectrum of the element
Wave/Particle Duality
 Louis DeBorglie
 Particles of matter behave like waves
  = h/p
Wave/Particle Duality
 Arthur Compton
 Light behaves like a particle
 Photons can collide with electrons and knock them off their
path because electrons are so small
Wave/Particle Duality
 Therefore… light behave as both a particle and a wave
 Therefore… electrons behave as both a particle and a wave
Heisenberg Uncertainty Principle
 It is impossible to know exactly both the velocity and position
of an electron at the same time.
Quantum Mechanical Model
 Heisenberg’s Uncertainty principle changes the modern
atomic model
 Instead of electrons moving around the nucleus on paths, the
electrons are like a cloud around the nucleus
 Similar to the propeller on a plane.
Atomic Orbitals
 An atomic orbital is a region of space in which there is a high
probability of finding an electron.
Electron Configurations
 An Electron configuration is similar to a map of where each
electron is likely located around the atom.
The four sublevels and their orbitals!!
s sublevel
 Number of Orbitals: 1
 Capacity: 2 electrons
p sublevel
 Number of Orbitals: 3
 Capacity: 6 electrons
d sublevel
 Number of Orbitals: 5
 Capacity: 10 electrons
f sublevel
 Number of Orbitals: 7
 Capacity: 14 electrons
3 Rules of Electron Configurations
 Aufbau Principle
 Electrons occupy the orbitals of lowest energy first.
3 Rules of Electron Configurations
 Pauli Exclusion Principle
 Each orbital can hold no more than two electrons and must
have opposite spins
3 Rules of Electron Configurations
 Hund’s Rule
 One electron must enter each orbital until all the orbitals
contain one electron. Then the electrons can be paired.